Adjustable tension force unit



3 Sheets-Sheet 1 m V M m Q mm M Wu. RM M W 1W m 2 h N n N n W ATTORNEYS Nov. 10, 1964 E. L. ZlVl ADJUSTABLE TENSION FORCE UNIT Filed Oct. 26, 1962 Nov. 10, 1964 E. L. ZlVl 3,156,430

ADJUSTABLE TENSION FORCE UNIT Filed 001:. 26, 1962 5 Sheets-Sheet 2 INVENTOR fan av 4. 2/14,

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ATTORNEYS Nov. 10, 1964 I E. L. ZlVl 3,156,430

ADJUSTABLE TENSION FORCE UNIT Filed Oct. 26, 1962 3 Sheets-Sheet 3 INVENTOR Eon 11v 4. 2/1,!)

United States Patent 3,156,430 ADJUSTABLE TENSION FORCE UNIT Edwin L. Zivi, Severna Park, Md, assignor to Arnetek, Inc, New York, N.Y., a corporation of Delaware Filed Oct. 26, 1962, Ser. No. 233,271 8 Claims. (Cl. 242-107) This invention relates to a force device for providing an adjustable or readily variable but substantially constant tractive force in a cable or equivalent means attached to an object to be stressed. The instant disclosure constitutes an improvement over the device disclosed in my co-pending application Ser. No. 781,551, filed December 19, 1958, now Patent No. 3,060,929. The motor power for this invention is obtained from a spring motor. A spring motor consists essentially of a spring wound on a drum and unwound onto a second drum. Such a spring may be a tightly coiled non-cumulative force spiral spring for example, of the type disclosed in Patent No. 2,609,191 or No. 2,609,192, wound on a drum with its extended portion reverse wound on a drum, to form what is known as a B motor which is disclosed in Fornelius Patent No. 1,977,546.

As noted in my earlier filed application, traction apparatus relied upon by way of explanation of the invention, to place a limb or other part of a human body under tension to temporarily overcome muscular contraction, involves a mechanical set-up of apparatus that is usually bulky and relatively complicated involving many component parts and requires considerable time and skill for its set-up on or about a patients bed. Moreover, the amount of this force is not easily and quickly varied.

The device of the present invention has many applications in exerting force for tensioning or counterbalancing equipment, for example, as applied to orthopedic tensioning in connection with which the invention will be described. In the latter application the invention is adapted to overcome these diliiculties and disadvantages and to provide a construction that is simple in its mechanical structure, relatively light in weight and compact, and one which does not require the exercise of considerable professional skill and ability by the user to install and use it. Additionally, the device can be readily adjusted to provide a plurality of relatively small changes in tractive force together with a doubling of each adjusted traction value without requiring removal of the unit from its installed position.

Accordingly, it is an object of this invention to provide a traction unit including a single substantially constant stress motor means, which is simple as to mechanical structure, light, portable and adapted to a wide range of application and use.

A further object is to provide a traction unit that is easily adjustable in output force and capable of exerting and maintaining a desired tractive force of substantially constant value.

A further object is a compact tensioning unit incorporating a single constant stress spring motor that will provide a wide array of different and substantially constant tension outputs and wherein these outputs may readily be doubled in value without dismounting the unit as a whole when installed in use.

The foregoing and other objects of the invention will become apparent from the following description taken in conjunction with the accompanying drawings which disclose a preferred embodiment and in which like numerals refer to like par-ts.

FIGURE 1 is a side elevational view of the entire traction unit.

FIGURE 2 is a sectional View taken along the line 2-2 of FIGURE 1.

3,156,430 Patented Nov. 10., 1964 FIGURE 3 is a plan view of the entire unit.

FIGURE 4 is a schematic side view of the output and take-up drums showing the relative disposition of the drums for replacement of a substituted cable drum of different diameter.

FIGURE 5 is a schematic plan view of the showing in FIGURE 4 with a substituted cable drum in position for mounting.

FIGURES 6A and 6B are schematic showings of the output drum with a cable drum of different diameters mounted therewith.

FIGURE 7 is a fragmentary view of a portion of the unit showing one way in which the unit is connected to an orthopedic traction cable.

FIGURE 8 is a view similar to FIGURE 7 showing another way in which the unit is connected to provide a doubled spring load on an orthopedic traction cable.

In the embodiment illustrated the frame member of the traction unit comprises a primary channel-shaped frame member A, the web portion 11 of which is of appreciably greater thickness than the parallel end flange portions 12 and 13. Suitably fixedly mounted on one end, as by threaded connections at 14 and 15, on web 11 are two shaft members 16 and 17 that are preferably of the same diameter that extend parallel to the flange end portions 12, 13 and lie in a common plane normal thereto.

Shaft 16, of a length considerably shorter than shaft 17, has a head 2% of enlarged diameter on its free end with a kerf 21 therein for reception of a mounting tool such as a screwdriver. Shaft 17, headless and of uniform diameter throughout, is provided with an annular groove 22 near its free end. On shaft 16 a spring take-up spool or drum 25, having an annular flange 26 at its end adjacent frame web 11, is mounted for free rotation between the shaft head lit and a spacing washer 27 which prevent endwise movement thereof. A spring output spool or drum 30 is mounted for free rotation on shaft 17, a spacing washer 31 being positioned between the inner face 32 of the drum and frame web 11. Power output drum 30 has an annular flange 33 at its edge remote from frame web 11, the respective drum flanges 33 and 26 being complementary to each other. Also mounted for free rotation on shaft 17 and extending within a concentric annular recess 35 in the outer face of drum 30 is another drum 36 held on shaft 17 and in engagement with the bottom of recess 35 in drum Si by means of a wire spring clip mounted generally chordwise on the outer face of drum 36 by suitable means such as screws 33, 39. An intermediate portion of wire 37 interengages a portion of shaft groove 22 which is disposed closely adjacent the plane of the outer face of the cable drum thereby locking both drums 30 and 36 onto shaft 17. Spring clip 37 provides for quick removal of drum 36 from shaft 17 whenever desired.

Spring drum 3% is provided with a counter-bored pas sage 44 disposed near and parallel to its peripheral circular face. Passage 40 comprises a section 41 of small diameter opening to the outer drum face while its section 42 of larger diameter opens to the inner face 32 of the drum. A traction cable 45 extends through an aperture 46 in frame end flange 12 and extends" around cable drum 36 and into portions 41 and 42 of passage 40 and is suitably anchored in the larger passage section 42 as by an enlargement 47 thereon or in any other suitable manner.

The power for the traction or pull on cable 45 is obtained from a coiled and pre-stressed spring 50 which is unattachably mounted at one end on drum 25 and which tends to coil up thereon when allowed to do so. The other end of coiled spring 50 is reversely coiled on and anchored in any suitable manner to the spring output drum 30.

A separate secondary frame structure B is normally disposed adjacent flange 12 of the primary frame A. Structure B consists of a frame having parallel side walls 54 and 55 connected together by a bottom wall 61 integral therewith. This frame, which initially was of square profile in elevation, has a vertical left-hand edge 69 disposed at right angles to the plane of bottom wall 61. In the upper edge of the frame walls 54, 55 is formed a step 63 between two horizontally extending portions 64 and 65 offset vertically relative to each other, the step 63 being located, as shown in FIGURE 1 near the left vertical edge 60. The lower edge portion 62 of the righthand edge portion of the frame is parallel to edge dti and is adapted to lie in contacting support relation to frame A when the unit is not in use. The upper right-hand edge portion 66 may be angularly inclined relative to portion 62.

The free end portion of cable 45 outwardly of aperture 46 of frame end wall 12 enters frame structure B between the two parallel side walls 54 and 55 at the side 2 adjacent side wall 12 of frame A. Cable 45 then is looped partially around a pulley 56, rotatably supported on a shaft 57 suitably supported in the frame side wall 54, 55, the end portion of the cable then extending out of the upper side of frame B with a suitable attaching hook member 58 having a transversely extending abutment bar member 59 formed at its base. The crossbar 59 is of a suificient length and size as to extend across and beyond walls 54, 55 and to abut and wedge between wall step 63 and the periphery of pulley 56 to prevent the end of the cable from being pulled down through and free of frame structure B by the tractive force of spring 50. Moreover, under certain conditions of operation to be described, bar 59 forms a means to connect the end of cable 45 to the secondary frame structure B. On the left end of bottom wall 61 of the secondary frame a ring or the like 70, for attachment of a cable means 71 connected to the object to be placed under tension by the unit, is mounted by means of an aperture 72 therein. Another attachment aperture 73 is provided in the upper end of frame A and wall 12 for connection of cable hook member 58 under certain conditions of operation to be described. The tension in cable 45 effected by spring 50 normally holds edge 62 of frame B in firm contact with the end wall 12 of frame A.

In use, the tension unit, comprised of both structures A and B, is mounted on any suitable support as by means of the attachment device 75 secured to the end wall 13 of frame structure A. With cable '71 connected, for example, to a patients leg that is to be placed under tension by the traction unit the secondary frame B is moved away from end wall 12 of frame A (FIGURE 7) in order to get the benefit of the full tractive force of the unit as well as to allow for some endwise movement of cable 71 due to some slight shifting of position by the patient. With the device used in the manner indicated in FEGURE 7, that is, with cross bar 59 of hook 58 wedged between step 63 and the periphery of pulley 56, the cables 45 and 71 act as a unitary single cable. The movement of frame B to the position described causes a clockwise rotation of output drum (FIGURE 1) since cable is acting in a clockwise direction thereon by means of the leverage R afforded it by the radius of cable drum 36.

As the transfer of the coiled pre-stressed spring 50.

takes place from take-up drum 25 to output drum 30 the spring coil is stressed in a direction reverse to its normal relaxed condition as it is pulled through zone 51 and then bent backwards around the drum 30. This develops a return driving force in the spring that causes it to naturally tend to re-reel itself clockwise back onto take-up drum During subsequent angular rotation of output drum 3-6 all of the spring already transferred to drum 369 does not change the stress value in the coiled spring and all of its portion remaining relaxed on the take-up drum is at virtually zero stress. Only the spring strip passing through zone 51 is subject to a change in stress. The entire length of the spring material during the winding or unwinding is stressed incremently in truly non-cumulative fashion and the torque produced by the arrangement of the coiled strip spring and drums as disclosed is substantially constant from the start to the completion of the driving cycle. Thus, this spring motor arrangement causes a substantially constant force to continuously act on cable 45 as it is pulled out of frame A as the spring strip is transferred from the take-up drum 25 to output drum 39. As the traction load on cable 45 is lessened, the cable is automatically re-wound on cable drum 36 as the prestressed spring strip tends to recoil and re-reel itself back onto the take-up drum due to its return driving power.

To adapt the cable drum and cable system for various tractive loadings for the above-described or any substantially constant rotative force, merely requires that spring drum 3% be rotated by tension on cable 45 to the position shown in FIGURE 4 whereby the cable is free of cabie drum 36. Spring clip 37 is removed from the annular groove 22 in shaft 17 to allow removal of the cable drum 36 from shaft 17 for replacement by another drum of different diameter, since the effective tractive force of the motor device is dependent on the radius of the cable drum, that is, its moment arm. FIGURES 1, 6A and 6B indicate the use of cable drums 36, 36', 36" of different radii R, R, R", respectively, it being assumed for simplicity that the same spring member is used in each instance. Thus, for example, with five cable drums of predetermined different diameters being provided and using the same basic traction device, employed in the manner described with respect to FIGURE 7, may have a constant output tension of 6, 7, 8, 9 or 10 pounds.

In order that the traction unit have greater flexibility for use with materially larger loadings without the necessity of making any further changes in the size of its component parts merely requires that hook 58 on the end of cable 45 be placed in engagement with aperture 73 in end wall 12 of frame A, as indicated in FIGURE 8. As is apparent from the physical laws pertaining to pulleys the tension in each reach x and y of cable 45 is equal to one half of the tractive force in the orthopedic or other cable 71. Thus for each of the five cable drums mentioned above the effective output tension of the basic traction unit transmitted to cable 71, when used in this manner, will now be doubled or, respectively, 12, 14, l6, 18 or 20 pounds. Obviously, the device is not limited for use with cable drums only of the specific diameters or number mentioned above by way of example since the size of the unit and its component parts may be of any desired size. Likewise, for the purpose of safety and general appearance frame unit A may be encased, if desired, in an enclosure or housing suitably secured thereon and provided with a closable opening therein abreast of recess 35 in spring output drum 3!! for the removal and replacement of the cable drums of different diameters.

From the foregoing description it will be apparent that the structure above described achieves the objects of the invention. However, it is obvious to those skilled in the art that certain changes, alterations, modifications, or substitutions may be made without departing from the spirit and scope as set out in the following claims.

What is claimed is:

l. A cable tensioning device for providing a tensile stress of a substantially constant but adjustable output value in a cable, comprising a base portion, a power output drum means mounted for rotation about a shaft mounted on said base portion, motor means to exert a substantially constant torque to rotate said power output drum means, a cable drum mounted for rotation on said shaft with said power output drum means, a cable, said cable being wrapped around said cable drum in a direction to be subjected to tension by the torque in said power output drum means, said cable having one end secured to said power output drum means, whereby when said cable is unreeled from said cable drum said cable drum is disengaged from said cable and may be removed from said shaft and another cable drum of any diameter placed on said shaft to vary the effective output of said device, the cable being reeled back onto said cable drum by the torque of said power output drum means.

2. A cable tensioning device as defined in claim 1 having means to releasably retain said cable drum on said shaft.

3. A cable tensioning device as defined in claim 1 in which flange means is provided on said removable cable drum to retain said cable.

4. A cable tensioning device as defined in claim 1 in which flange means is provided on the outer side of said cable drum to retain said cable.

5. A cable tensioning device as defined in claim 2 in which the cable drum is held securely against said power output drum means by said retaining means.

6. A cable tensioning device as defined in claim 2 in which the cable drum is held securely against the power output means within a recess in said power output means.

7. A cable tensioning device in accordance with claim 1 having a pulley, means mounting the pulley for rotation, the other end of the cable extending about a portion of said pulley, stop means to prevent the disengagement of the cable from the pulley, means to detachably secure the said other end of the cable to the base portion, and means to move the mounting means away from the base portion.

8. A cable tensioning device in accordance with claim 1 having a pulley, means mounting the pulley for rotation, the other end of the cable extending about a portion of said pulley, stop means to prevent the disengagement of the cable from the pulley, means including a hook to detachably secure the said other end of the cable to the base portion, and means to move the mounting means away from the base portion.

References Cited by the Examiner UNITED STATES PATENTS 458,938 9/91 Bloomfield 242107 973,553 10/10 Peacock 242107 2,559,050 7/51 St. Clair 242107.3 2,673,694 3/54 Howell 242107.3 3,061,234 10/62 Morey 242-107.l 3,085,768 4/63 Treutelaar 242107 MERVIN STEIN, Primary Examiner. 

1. A CABLE TENSIONING DEVICE FOR PROVIDING A TENSILE STRESS OF A SUBSTANTIALLY CONSTANT BUT ADJUSTABLE OUTPUT VALUE IN A CABLE, COMPRISING A BASE PORTION, A POWER OUTPUT DRUM MEANS MOUNTED FOR ROTATION ABOUT A SHAFT MOUNTED ON SAID BASE PORTION, MOTOR MEANS TO EXERT A SUBSTANTIALLY CONSTANT TORQUE TO ROTATE SAID POWER OUTPUT DRUM MEANS, A CABLE DRUM MOUNTED FOR ROTATION ON SAID SHAFT WITH SAID POWER OUTPUT DRUM MEANS, A CABLE, SAID CABLE BEING WRAPPED AROUND SAID CABLE DRUM IN A DIRECTION TO BE SUBJECTED TO TENSION BY THE TORQUE IN SAID POWER OUTPUT DRUM MEANS, SAID CABLE HAVING ONE END SECURED TO SAID POWER OUTPUT DRUM MEANS, WHEREBY WHEN SAID CABLE IS UNREELED FROM SAID CABLE DRUM SAID CABLE DRUM IS DISENGAGED FROM SAID CABLE AND MAY BE REMOVED FROM SAID SHAFT AND ANOTHER CABLE DRUM OF ANY DIAMETER PLACED ON SAID SHAFT TO VARY THE EFFECTIVE OUTPUT OF SAID DEVICE, THE CABLE BEING REELED BACK ONTO SAID CABLE DRUM BY THE TORQUE OF SAID POWER OUTPUT DRUM MEANS. 